<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>demo-1</title>

    <meta name="viewport" content="width=device-width, initial-scale=1">
    <link rel="stylesheet" href="../node_modules/bootstrap/dist/css/bootstrap.css">

    <style>
        div{
            border: 2px solid #000000;
        }
    </style>
</head>
<body>
    <div class="container">
        <div class="row">
            <div class="col-xs-6 col-sm-3">.col-xs-6 .col-sm-3</div>
            <div class="col-xs-6 col-sm-3">.col-xs-6 .col-sm-3</div>

            <!-- Add the extra clearfix for only the required viewport -->
            <!--<div class="clearfix visible-xs-block"></div>-->

            <div class="col-xs-6 col-sm-3">.col-xs-6 .col-sm-3</div>
            <div class="col-xs-6 col-sm-3">.col-xs-6 .col-sm-3</div>
        </div>
    </div>

</body>
</html>